The bolt stop is disposed in many guns having a bolt which compresses a spring (simply, referred to as the bolt spring in this document) acting on the bolt in response to a gun operation, and which moves forward in response to the released pressure. An automatic loading firearm which is so-called assault rifle includes this mechanism. In this type of gun, the bolt moves forward so as to load a bullet. After last bullet shooting, the bolt stops by colliding with the bolt stop in order to notify a user that the bullets are all shot. This operation of collision and stop is repeatedly performed every time the bullets are all shot.
Therefore, every time the bolt collides with the bolt stop, a strong impact is applied to the bolt stop. Consequently, metal fatigue is likely to occur, thereby causing damage to the bolt stop in the worst case. In a case of a real gun, this problem has been pointed out for a long time. However, at the present time, no idea can be found about what kind of remedial measures has to be planned. That is, it is not possible to find a recognizable gun in which damage prevention measures are planned for the bolt stop.
Even if the related art is examined, an intended result cannot be obtained. For example, through a text search site of the Japanese Patent Office, only 3 search results are obtained by using the bolt stop as a keyword. One of the results relates to an internal combustion engine, and the other two results are also irrelevant to an aspect of the bolt stop which is an object of the present invention. Japanese Unexamined Patent Application Publication No. 2010-025501 discloses an invention of a mechanical power supply stop device in an electric gun according to an application of the present applicant, and the bolt stop is referred to in the description. However, the disclosed electric gun imitates a real gun as a component. In fact, the disclosed electric gun only has a reset function. The other remaining one result in PCT Japanese Translation Patent Publication No. 2000-508051 discloses an invention relating to a bolt firing pin locking device of a firearm. In the description with reference to FIG. 2, there is a phrase such as “a bolt 14 can move rearward as far as a slight distance until a stop wall 25W comes into contact with a bolt stop surface 31f”, and a phrase such as “the bolt 14 is pressed against a bullet C by a large reaction spring (not illustrated) linked to the bolt 14 via a circular column 35” is described at the end of the sentence. However, these phrases in the description indicate that the impact applied to the bolt stop by the bolt is not an issue.
Furthermore, after US Patent Publications are examined by using the bolt stop as the keyword through a site of the US Patent and Trademark Office, approximately 10 results are obtained. Among these results, two inventions relating to the bolt stop of the firearm are found. In the two inventions, US2010/0275485A1 discloses an invention relating to the bolt stop employing a both-handed type so that the bolt stop can be used for a left-handed person, similarly to a right-handed person. In addition, US2005/0183310A1 discloses an invention in which a magazine is attached and detached in association with the bolt stop. Both of these do not disclose that the impact of the bolt is regarded as a problem.